Large scale industrial processing of citrus fruits into juices, canned fruit, fruit salads and other food products generates large volumes of citrus peels as a byproduct. The entire peeling process may be performed manually with specialized knives or mechanically with equipment such as citrus fruit juicers. Many vesicles—juice sacs—are left attached to a citrus peel. Much of citrus mill effluents—peel, rag, seed, pulp, etc.—are dewatered, chopped, kiln dried, or sold as animal feed. It is however well known that citrus peels contain useful and edible components. There is an ongoing commercial interest in identifying uses for left over citrus peels and reducing the environmental impact posed by waste from citrus processing.
As people are becoming more health conscious, interest in dietary fiber intake has increased. Dietary fibers from other fiber sources are used more frequently than those from fruit; however, fruit fiber is a high quality dietary fiber. As compared to other forms of fiber, fruit fiber has a higher total and soluble fiber content, water binding capacity, oil absorbing capacity, and colonic fermentability, as well as lower phytic acid content and caloric value. For example, residues from orange juice extraction are recognized as a potentially excellent source of dietary fiber because this material is rich in pectin and is available in large quantities. Citrus-derived fruit fibers are expected to have better quality than other dietary fibers because of the presence of bioactive compounds, such as flavonoids, polyphenols, and carotenes.
Intact citrus peels comprise two regions—albedo and flavedo. Albedo is known for its dietary fiber content including sugar, cellulose, and pectic substances. It has been used as a filler material to fortify stock food. Flavedo is known for containing Vitamin A, carotenes, and xanthophylls. It has been used as a coloring agent in the preparation of food stuffs, a clouding agent in fruit juice drinks, and a fortifier of livestock feed and human food. Dried citrus peels or pulp by-products and waste, which are highly absorptive, have been used as poultry bedding.
Citrus fruit by-products, such as the peels and pulp, can be processed in many different ways to obtain food or feed additives. For example, U.S. Pat. No. 4,225,625 teaches a method for separating citrus peels into separate albedo and flavedo components for later use. In the invention taught by U.S. Pat. No. 7,060,313, citrus peel and pulp with juice removed are processed to recover components of value such as, d-limonene, molasses, pectin pomace, and food grade quality peel mass. Other methods convert dried citrus peels to animal feed, as taught by U.S. Pat. No. 2,186,907, and to food additives, as taught by U.S. Pat. No. 3,868,466. Yet another example of converting citrus by-products is provided by U.S. Pat. No. 7,629,010 which teaches methods for recovering citrus fiber from citrus vesicles using organic solvents to obtain a food additive for beverages, baked goods, meat or meat emulsions, confectionary, jams, jellies. This method uses organic solvents, as does the method taught by U.S. Pat. No. 6,183,806 for making citrus fruit peel extracts and flour. Collecting citrus oil, as taught by U.S. Pat. No. 6,151,799, is another way to process useful components from citrus peels.
Citrus processing creates substantial waste in the form of peels, seeds, rag, and pulp. The U.S. regulatory environment places restrictions on disposal of waste emissions from citrus plants. As a consequence, citrus peel waste cannot be dumped into landfills, but must be converted into useable products, such as stock feed. The conversion is a costly add-on expense for citrus plant operators.
The foregoing is believed to describe the prior art processes. While the above prior art processes provide for extracting citrus by-products for use, one drawback of the prior art is that the processes are costly and impractical because unnecessary processing steps are used, for example, separating albedo from flavedo of citrus peels. Another drawback is the need to use pollution generating solvents to extract components of citrus by-products. A further drawback is that unnecessary processing and pollution generating solvent-based processing increase operating costs and maintenance. Furthermore, the use of pollution generating solvents requires operational control to meet regulatory framework and could have an adverse impact on the environment.
This invention overcomes the drawbacks of the prior art. This invention provides processes to convert standard citrus waste—a high biochemical oxygen demand (B.O.D.) product—into value added commercial products, to reduce or eliminate discharge problems associated with industrial waste, to drastically reduce discharge and penalty costs for handling waste, and to provide a water-based process thus eliminating the use of environmental pollutants such as organic solvents.